Prior technologies relating to reflective color displays have, in general, used red/green/blue (RGB) colors. In the RGB color displays, each pixel is broken down into three or four sub-pixels and each sub-pixel has a red filter, blue filter, green filter or no filter over a black and white reflective medium. By selectively turning sub-pixels on or off, a full color spectrum may be achieved. For example, the white state is achieved by turning on all three RGB sub-pixels. Because each of the RGB sub-pixels occupies ⅓ of the white spectrum, the maximum reflectivity of each sub-pixel is about ⅓ of the reflectivity of the white color. The maximum brightness of each of the RGB colors therefore is ⅓ of the white color since the sub-pixels of the other two colors are turned off. In practice, a reflective display actually achieves substantially less than this theoretical brightness.
Over the years, many pixel architectures have evolved, including adding two green sub-pixels or a white sub-pixel to gain some brightness at the expense of color saturation. However, in general, the RGB color system shows very limited whiteness and poor color brightness.
U.S. Pat. No. 7,046,228 discloses an electrophoretic display device having a dual switching mode which allows the charged pigment particles in a display cell to move in either the vertical (up/down) direction or the planar (left/right) direction. U.S. patent application Ser. No. 12/370,485 discloses an alternative multiple color display. In both cases, display cells are filled with a dyed fluid having white particles dispersed therein and each of the display cells is capable of displaying three color states, i.e., the color of the charged pigment particles, the color of the dielectric solvent or solvent mixture or the background color of the display cell. These two types of the display can provide RGB color states which are as bright as those achieved by the RGB type display. They, in addition, can also provide non-compromised white and black color states which could not be achieved by the RGB type display.